Public servants operate under "Codes of Ethics" and "Guidelines" and all other forms of Buzz words for the rules.
Some of them are pedantic and excessive. Take for example ones forcing a public sector employee to record "gifts" over a certain value, and that decrees gifts to be public property (Ie, if the employee wants to use the gift for their personal use, then they have to "buy" the gift from the employer at the fair market value). Take the ones that decree that FF points are not to be acrued for travel, or that FF points earnt on official travel cannot be used for upgrades Etc. This is all done to provide accountability and proper use of taxpayer funds (aka, the "avoid front page of the newspaper" syndrome)
While people may not agree with the rules, these are a core component of the guidelines that a public sector employee works under. Not declare a gift of a certain value? It can lead to investigation, sanctions or dismissal (or possibly even criminal charges if the corruption/bribery is suspected). Claim FF points on a piece of travel where the guidelines tell you not to? Same story.
I don't see how previous landmark court decisions affect contracts between individuals and their employer where the contract sets down a set of rules that are not "unjust". (Well they may be unjust to some, but I doubt the court sees it that way).